By Pankaj, US correspondent, [RxPG] Staphylococcus aureus causes a wide variety of diseases including boils and furuncles and more serious diseases such as septicemia and pneumonia, and a debate has long raged about the existence of S. aureus "superbugs"  more dangerous strains that may be associated with particularly invasive disease.

In the December 15 issue of the Journal of Clinical Investigation, Damian Melles and colleagues from University Medical Center Rotterdam examined 829 S. aureus strains from healthy donors from the city of Rotterdam. The genetic relatedness of the strains was compared and revealed the existence of 3 major and 2 minor genetic clusters. These clusters corresponded to the predominant genetic groups identified in a similar analysis recently performed in the United Kingdom, indicating that the same clonal lineages of the organism appear to be dominant in 2 distinct geographic locations.

Surprisingly, while the 2003 UK-based study found no evidence of hypervirulent clones or "superbugs" assocated with particularly invasive forms of disease, Melles et al. examined isolates from individuals with bacteriemia, deep-seated abscesses, or impetigo and found clear evidence that some strains of S. aureus are more virulent that others in that they appear more frequently in people with serious S. aureusrelated disease that healthy individuals that simply carry the organism without falling prey to infection.

In an accompanying commentary, Timothy Foster from Trinity College, Dublin, discusses some potential reasons for the discrepancies between the Dutch and UK studies, the growing problem of antibiotic resistance, and reiterates the conclusion that while all strains of S. aureus have the potential to cause infection, some appear to be more virulent that others.